When hygroscopic materials are to be dispensed through a manufacturing process, wherein, for example, the materials are heated, pressurized and extruded, it is desirable, usually necessary, to dry the materials before they are passed through the manufacturing process. Many of the materials which are purchased by the processor for further processing are in the form of solid particles, such as beads, pellets or chips. As the particles pass through a critical temperature range, if the particles are in physical contact with one another, frequently they tend to cling together and do not flow readily. Therefore, when the particles are dispensed from a hopper, the clinging together of the particles tends to plug the hopper.
In the past, the drying of such particulate materials has been performed at a temperature level below the critical temperature range of the material so as to avoid the problem of plugging the storage dispenser, or, in the alternative, the material has been heated to a temperature level above the critical range of temperatures and simultaneously agitated to prevent the particles from clinging together, so that once the particles have been heated through the critical temperature range, the particles could be stored, allowed to cool, and when the particles were to be processed, the particles could be transferred to a dispensing hopper where they are dried at elevated temperatures prior to the step of processing the particles.
In the first situation, where the upper drying temperature level is maintained at a low temperature to avoid instability of the particles, the drying procedure is relatively slow and requires a large hopper, and the material being processed is delivered to the processing machine at a relatively low temperature and not in the most desirable condition for further processing. In the second situation where the material is heated and agitated by a separate piece of equipment through the critical temperature range, the separate equipment is expensive to purchase and maintain, and the operation of the equipment requires energy and operator time.